深入玩转K8S之使用kubeadm安装Kubernetes v1.10以及常见问题解答

原文链接：http://blog.51cto.com/devingeng/2096495

关于K8S：

Kubernetes是Google开源的容器集群管理系统。它构建于docker技术之上，为容器化的应用提供资源调度、部署运行、服务发现、扩容缩容等整一套功能，本质上可看作是基于容器技术的mini-PaaS平台。

相信看过我博客的童鞋应该知道，我在14年的时候就发表了一篇名为Docker容器管理之Kubernetes当时国内Docker刚刚兴起，对于Docker的兴起我很有感触，仿佛一瞬间就火了，当时也是一个偶然的机会了解到K8S，所以当时就写文简单的介绍了下K8S以及如何采用源码部署。今时不同往日K8S在容器界已经是翘首，再读旧文有感而发，索性来研究下kubeadm安装K8S以及Dashboard功能预览。

环境描述：

采用CentOS7.4 minimual，docker 1.13，kubeadm 1.10.0，etcd 3.0， k8s 1.10.0

我们这里选用三个节点搭建一个实验环境。

10.0.100.202 k8smaster

10.0.100.203 k8snode1

10.0.100.204 k8snode2

准备环境：

1.配置好各节点hosts文件

2.关闭各节点系统防火墙

3.关闭各节点SElinux

4.关闭各节点swap

5.配置各节点系统内核参数使流过网桥的流量也进入iptables/netfilter框架中，在/etc/sysctl.conf中添加以下配置：

net.bridge.bridge-nf-call-iptables = 1net.bridge.bridge-nf-call-ip6tables = 1sysctl -p

使用kubeadm安装：

1.首先配置各节点阿里K8S YUM源

cat <<EOF > /etc/yum.repos.d/kubernetes.repo[kubernetes]
name=Kubernetes
baseurl=https://mirrors.aliyun.com/kubernetes/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=0EOFyum -y install epel-releaseyum clean allyum makecache

2.在各节点安装kubeadm和相关工具包

yum -y install docker kubelet kubeadm kubectl kubernetes-cni

3.启动Docker与kubelet服务

systemctl enable docker && systemctl start dockersystemctl enable kubelet && systemctl start kubelet

提示：此时kubelet的服务运行状态是异常的，因为缺少主配置文件kubelet.conf。但可以暂不处理，因为在完成Master节点的初始化后才会生成这个配置文件。

4.下载K8S相关镜像（Master节点操作）

因为无法直接访问gcr.io下载镜像，所以需要配置一个国内的容器镜像加速器

配置一个阿里云的加速器：

在页面中找到并点击镜像加速按钮，即可看到属于自己的专属加速链接，选择Centos版本后即可看到配置方法。

提示：在阿里云上使用 Docker 并配置阿里云镜像加速器，可能会遇到 daemon.json 导致 docker daemon 无法启动的问题，可以通过以下方法解决。

你需要的是编辑 vim /etc/sysconfig/docker 然后 OPTIONS='--selinux-enabled --log-driver=journald --registry-mirror=http://xxxx.mirror.aliyuncs.com'
registry-mirror 输入你的镜像地址 最后 service docker restart 重启 daemon 然后 ps aux | grep docker 然后你就会发现带有镜像的启动参数了。

5.下载K8S相关镜像

OK，解决完加速器的问题之后，开始下载k8s相关镜像，下载后将镜像名改为k8s.gcr.io/开头的名字，以便kubeadm识别使用。

#!/bin/bash
images=(kube-proxy-amd64:v1.10.0 kube-scheduler-amd64:v1.10.0 kube-controller-manager-amd64:v1.10.0 kube-apiserver-amd64:v1.10.0
etcd-amd64:3.1.12 pause-amd64:3.1 kubernetes-dashboard-amd64:v1.8.3 k8s-dns-sidecar-amd64:1.14.8 k8s-dns-kube-dns-amd64:1.14.8
k8s-dns-dnsmasq-nanny-amd64:1.14.8)
for imageName in ${images[@]} ; dodocker pull keveon/$imageNamedocker tag keveon/$imageName k8s.gcr.io/$imageNamedocker rmi keveon/$imageName
done

上面的shell脚本主要做了3件事，下载各种需要用到的容器镜像、重新打标记为符合k8s命令规范的版本名称、清除旧的容器镜像。

提示：镜像版本一定要和kubeadm安装的版本一致，否则会出现time out问题。

6.初始化安装K8S Master

执行上述shell脚本，等待下载完成后，执行kubeadm init

[root@k8smaster ~]# kubeadm init --kubernetes-version=v1.10.0 --pod-network-cidr=10.244.0.0/16
[init] Using Kubernetes version: v1.10.0
[init] Using Authorization modes: [Node RBAC]
[preflight] Running pre-flight checks.[WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service'[WARNING FileExisting-crictl]: crictl not found in system path
Suggestion: go get github.com/kubernetes-incubator/cri-tools/cmd/crictl
[preflight] Starting the kubelet service
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [k8smaster kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.0.100.202]
[certificates] Generated apiserver-kubelet-client certificate and key.
[certificates] Generated etcd/ca certificate and key.
[certificates] Generated etcd/server certificate and key.
[certificates] etcd/server serving cert is signed for DNS names [localhost] and IPs [127.0.0.1]
[certificates] Generated etcd/peer certificate and key.
[certificates] etcd/peer serving cert is signed for DNS names [k8smaster] and IPs [10.0.100.202]
[certificates] Generated etcd/healthcheck-client certificate and key.
[certificates] Generated apiserver-etcd-client certificate and key.
[certificates] Generated sa key and public key.
[certificates] Generated front-proxy-ca certificate and key.
[certificates] Generated front-proxy-client certificate and key.
[certificates] Valid certificates and keys now exist in "/etc/kubernetes/pki"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/admin.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/kubelet.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/controller-manager.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/scheduler.conf"
[controlplane] Wrote Static Pod manifest for component kube-apiserver to "/etc/kubernetes/manifests/kube-apiserver.yaml"
[controlplane] Wrote Static Pod manifest for component kube-controller-manager to "/etc/kubernetes/manifests/kube-controller-manager.yaml"
[controlplane] Wrote Static Pod manifest for component kube-scheduler to "/etc/kubernetes/manifests/kube-scheduler.yaml"
[etcd] Wrote Static Pod manifest for a local etcd instance to "/etc/kubernetes/manifests/etcd.yaml"
[init] Waiting for the kubelet to boot up the control plane as Static Pods from directory "/etc/kubernetes/manifests".
[init] This might take a minute or longer if the control plane images have to be pulled.
[apiclient] All control plane components are healthy after 21.001790 seconds
[uploadconfig] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[markmaster] Will mark node k8smaster as master by adding a label and a taint
[markmaster] Master k8smaster tainted and labelled with key/value: node-role.kubernetes.io/master=""
[bootstraptoken] Using token: thczis.64adx0imeuhu23xv
[bootstraptoken] Configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstraptoken] Configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstraptoken] Configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[bootstraptoken] Creating the "cluster-info" ConfigMap in the "kube-public" namespace
[addons] Applied essential addon: kube-dns
[addons] Applied essential addon: kube-proxyYour Kubernetes master has initialized successfully!To start using your cluster, you need to run the following as a regular user:mkdir -p $HOME/.kubesudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/configsudo chown $(id -u):$(id -g) $HOME/.kube/configYou should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:https://kubernetes.io/docs/concepts/cluster-administration/addons/You can now join any number of machines by running the following on each node
as root:kubeadm join 10.0.100.202:6443 --token thczis.64adx0imeuhu23xv --discovery-token-ca-cert-hash sha256:fa7b11bb569493fd44554aab0afe55a4c051cccc492dbdfafae6efeb6ffa80e6

提示：选项--kubernetes-version=v1.10.0是必须的，否则会因为访问google网站被墙而无法执行命令。这里使用v1.10.0版本，刚才前面也说到了下载的容器镜像版本必须与K8S版本一致否则会出现time out。

上面的命令大约需要1分钟的过程，期间可以观察下tail -f /var/log/message日志文件的输出，掌握该配置过程和进度。上面最后一段的输出信息保存一份，后续添加工作节点还要用到。

7.配置kubectl认证信息（Master节点操作）

# 对于非root用户
mkdir -p $HOME/.kubesudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/configsudo chown $(id -u):$(id -g) $HOME/.kube/config# 对于root用户
export KUBECONFIG=/etc/kubernetes/admin.conf也可以直接放到~/.bash_profileecho "export KUBECONFIG=/etc/kubernetes/admin.conf" >> ~/.bash_profile

8.安装flannel网络（Master节点操作）

mkdir -p /etc/cni/net.d/cat <<EOF> /etc/cni/net.d/10-flannel.conf
{
“name”: “cbr0”,
“type”: “flannel”,
“delegate”: {
“isDefaultGateway”: true
}
}EOFmkdir /usr/share/oci-umount/oci-umount.d -pmkdir /run/flannel/cat <<EOF> /run/flannel/subnet.env
FLANNEL_NETWORK=10.244.0.0/16
FLANNEL_SUBNET=10.244.1.0/24
FLANNEL_MTU=1450
FLANNEL_IPMASQ=trueEOFkubectl apply -f https://raw.githubusercontent.com/coreos/flannel/v0.9.1/Documentation/kube-flannel.yml

9.让node1、node2加入集群

在node1和node2节点上分别执行kubeadm join命令，加入集群：

[root@k8snode1 ~]# kubeadm join 10.0.100.202:6443 --token thczis.64adx0imeuhu23xv --discovery-token-ca-cert-hash sha256:fa7b11bb569493fd44554aab0afe55a4c051cccc492dbdfafae6efeb6ffa80e6
[preflight] Running pre-flight checks.[WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service'[WARNING FileExisting-crictl]: crictl not found in system path
Suggestion: go get github.com/kubernetes-incubator/cri-tools/cmd/crictl
[discovery] Trying to connect to API Server "10.0.100.202:6443"
[discovery] Created cluster-info discovery client, requesting info from "https://10.0.100.202:6443"
[discovery] Requesting info from "https://10.0.100.202:6443" again to validate TLS against the pinned public key
[discovery] Cluster info signature and contents are valid and TLS certificate validates against pinned roots, will use API Server "10.0.100.202:6443"
[discovery] Successfully established connection with API Server "10.0.100.202:6443"This node has joined the cluster:
* Certificate signing request was sent to master and a responsewas received.
* The Kubelet was informed of the new secure connection details.Run 'kubectl get nodes' on the master to see this node join the cluster.

提示：细心的童鞋应该会发现，这段命令其实就是前面K8S Matser安装成功后我让你们保存的那段命令。

默认情况下，Master节点不参与工作负载，但如果希望安装出一个All-In-One的k8s环境，则可以执行以下命令，让Master节点也成为一个Node节点：

kubectl taint nodes --all node-role.kubernetes.io/master-

10.验证K8S Master是否搭建成功（Master节点操作）

# 查看节点状态
kubectl get nodes# 查看pods状态
kubectl get pods --all-namespaces# 查看K8S集群状态
kubectl get cs

常见错误解析

安装时候最常见的就是time out，因为K8S镜像在国外，所以我们在前面就说到了提前把他下载下来，可以用一个国外机器采用habor搭建一个私有仓库把镜像都download下来。

[root@k8smaster ~]# kubeadm init
[init] Using Kubernetes version: v1.10.0
[init] Using Authorization modes: [Node RBAC]
[preflight] Running pre-flight checks.[WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service'[WARNING FileExisting-crictl]: crictl not found in system path
Suggestion: go get github.com/kubernetes-incubator/cri-tools/cmd/crictl
[preflight] Starting the kubelet service
[certificates] Generated ca certificate and key.
[certificates] Generated apiserver certificate and key.
[certificates] apiserver serving cert is signed for DNS names [k8smaster kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 10.0.100.202]
[certificates] Generated apiserver-kubelet-client certificate and key.
[certificates] Generated etcd/ca certificate and key.
[certificates] Generated etcd/server certificate and key.
[certificates] etcd/server serving cert is signed for DNS names [localhost] and IPs [127.0.0.1]
[certificates] Generated etcd/peer certificate and key.
[certificates] etcd/peer serving cert is signed for DNS names [k8smaster] and IPs [10.0.100.202]
[certificates] Generated etcd/healthcheck-client certificate and key.
[certificates] Generated apiserver-etcd-client certificate and key.
[certificates] Generated sa key and public key.
[certificates] Generated front-proxy-ca certificate and key.
[certificates] Generated front-proxy-client certificate and key.
[certificates] Valid certificates and keys now exist in "/etc/kubernetes/pki"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/admin.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/kubelet.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/controller-manager.conf"
[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/scheduler.conf"
[controlplane] Wrote Static Pod manifest for component kube-apiserver to "/etc/kubernetes/manifests/kube-apiserver.yaml"
[controlplane] Wrote Static Pod manifest for component kube-controller-manager to "/etc/kubernetes/manifests/kube-controller-manager.yaml"
[controlplane] Wrote Static Pod manifest for component kube-scheduler to "/etc/kubernetes/manifests/kube-scheduler.yaml"
[etcd] Wrote Static Pod manifest for a local etcd instance to "/etc/kubernetes/manifests/etcd.yaml"
[init] Waiting for the kubelet to boot up the control plane as Static Pods from directory "/etc/kubernetes/manifests".
[init] This might take a minute or longer if the control plane images have to be pulled.Unfortunately, an error has occurred:timed out waiting for the conditionThis error is likely caused by:- The kubelet is not running- The kubelet is unhealthy due to a misconfiguration of the node in some way (required cgroups disabled)- Either there is no internet connection, or imagePullPolicy is set to "Never",so the kubelet cannot pull or find the following control plane images:- k8s.gcr.io/kube-apiserver-amd64:v1.10.0- k8s.gcr.io/kube-controller-manager-amd64:v1.10.0- k8s.gcr.io/kube-scheduler-amd64:v1.10.0- k8s.gcr.io/etcd-amd64:3.1.12 (only if no external etcd endpoints are configured)If you are on a systemd-powered system, you can try to troubleshoot the error with the following commands:- 'systemctl status kubelet'- 'journalctl -xeu kubelet'
couldn't initialize a Kubernetes cluster

那出现这个问题大部分原因是因为安装的K8S版本和依赖的K8S相关镜像版本不符导致的，关于这部分排错可以查看/var/log/message我们在文章开始安装的时候也提到了要多看日志。

还有些童鞋可能会说，那我安装失败了，怎么清理环境重新安装啊？下面教大家一条命令：

kubeadm reset

好了，至此就完成了K8S三节点集群的安装部署。

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